The present invention relates to a method for preparing corn fiber oil involving separating corn fiber from corn kernels (e.g., by a wet milling process), drying the corn fiber, grinding the dried corn fiber to produce ground corn fiber having a particle size of less than about 100 microns, combining the ground corn fiber with an aqueous solution having a specific gravity effective to float aleurone cells, removing the floating aleurone fraction, drying the aleurone fraction to form a dried aleurone fraction, grinding the dried aleurone fraction to form a ground aleurone fraction, extracting corn fiber oil from the ground aleurone fraction by means selected from the group consisting of an organic solvent and supercritical fluid extraction, and separating the extracted corn fiber oil from the extraction medium. The present invention also relates to a method of recovering corn aleurone cells from corn fiber involving separating corn fiber from corn kernels by a wet milling process, drying the corn fiber, grinding the dried corn fiber to produce ground corn fiber having a particle size of less than about 100 microns, combining the ground corn fiber with an aqueous solution having a specific gravity effective to float aleurone cells, and removing the floating aleurone fraction.
Corn (maize) fiber oil contains unique compounds called phytosterols that have been shown to have nutraceutical properties (U.S. Pat. No. 5,843,499 which is incorporated by reference in its entirety). Due to their nutraceutical value, commercial corn fiber oil-based products can potentially be sold for $11 to $22/kg ($5 to $10/lb) based on the current market retail price of products similar to corn fiber oil. The amount of oil in corn fiber is very low, approximately 1.5 to 3.0%. Due to the low concentration of oil in corn fiber, the extraction of the oil and its phytosterol compounds is not efficient and can be expensive. Singh et al. (Cereal Chem., 78(4): 436–441 (2001)) showed that more than 90% of the corn fiber oil comes from the aleurone layer, which is approximately 40% of the coarse (pericarp) fiber fraction. Among the different classes of phytosterol compounds present in the corn fiber oil, more than 95% of the ferulate phytosterol esters (FPE), 60% of free phytosterols (St) and 90% of fatty acyl phytosterol esters (St:E) are present in the oil recovered from the aleurone layer (Cereal Chem., 78(4): 436–441 (2001)).
The aleurone layer in most yellow dent corn hybrids is a single layer of cells located directly beneath the pericarp tissue (Watson, S. A., 1984, Corn and sorghum starches: Production, pages 417–468, in: Starch: Chemistry and Technology, R. L. Whistler, J. N. BeMiller, and E. F. Paschall, eds., Academic Press, Orlando, Fla.). During the conventional corn wet milling process the aleurone layer ends up in the fiber fraction.
The present study tested whether the aleurone layer could provide an enriched source of corn fiber oil and phytosterol compounds by attempting to separate the aleurone layer from other parts of the wet milled fiber fraction. Higher concentration of oil and phytosterol could make the extraction more efficient and less expensive. In the present study an effort was made to increase the concentration of the oil and phytosterols in corn fiber by floatation of the fiber tissue associated with the oil bodies (aleurone cells) in the fiber fraction.